Frail and unrepentant: Top Khmer Rouge leaders appear in court to argue for release as they await genocide trial

Three top Khmer Rouge leaders made a joint appearance before a UN-backed war crimes court today to seek release from custody as they await trial for genocide.

'Brother Number Two' Nuon Chea and ex-social affairs minister Ieng Thirith looked frail as they sat in the courtroom with former head of state Khieu Samphan.

There are strong concerns that not all of the defendants, who are aged between 78 and 85, will live to see a verdict.

On the stand: 'Brother Number Two' Nuon Chea listens in court and, right, former head of the Khmer Rouge state Khieu Samphan has headphones on

Custody: Khmer Rouge 'First Lady' Ieng Thirith, a former social affairs minister, left the court hearing early

They are accused of war crimes, crimes against humanity, genocide and other charges under Cambodian laws in connection with the deaths of up to two million people between 1975 and 1979 as a result of starvation, overwork and execution.

Lawyers called for their 'immediate release', claiming their detention was illegal because they had not been brought to trial four months after their indictments were issued.

Jasper Pauw, defending, said 'there are no conceivable reasons to keep Nuon Chea in custody'.

A pale Ieng Thirith, described as the 'First Lady' of the Khmer Rouge, left the courtroom as soon as proceedings began and waived her right to attend the hearing.

Nuon Chea - who wore sunglasses to protect his eyes from the light - suffered a dizzy spell and was sent to the court's detention facility on medical advice.

Genocide: Buddhist monks line up at the entrance of the Extraordinary Chambers in the Courts of Cambodia in Phnom Penh, Cambodia

Charges: Cambodian police officers guard the entrance to the court. The trial is expected to take months

Fellow accused Ieng Sary, the regime's foreign minister, did not attend the hearing. His lawyers claim he was too ill to spend full days in court.

All four defendants have been detained since they were arrested in 2007.

Prosecutors dismissed the call for their release and said they could try to escape the country or exert pressure on witnesses if freed.

Andrew Cayley, prosecuting, said: 'The passage of time has not diminished the impact of these crimes.'

A ruling on the request will be made in mid-February, but they are unlikely to be freed because of the uproar it would cause in Cambodia.

Horror: The Khmer Rouge regime killed two million people between 1975 and 1979 as it tried to create an agrarian utopia

Chab Chhean, 60, who lost 12 relatives under the regime, said outside court: 'The court must not release them because they abused the people so much.'

The trial, the tribunal's second, is due to start in the next five months and is expected to be lengthy as all four leaders dispute the charges against them.

It follows the landmark conviction in July of former Tuol Sleng prison chief Kaing Guek Eav, known as Duch, for war crimes and crimes against humanity for his role in the deaths of around 15,000 men, women and children.

The court, which does not have the power to impose the death penalty, handed Duch a 30-year jail term - but he could walk free in 19 years because of time already served.

Both Duch, 68, and the prosecution have appealed against the sentence.

Led by 'Brother Number One' Pol Pott, who died in 1998, the Marxist Khmer Rouge regime emptied entire cities in the late 1970s in a bid to create an agrarian utopia.